how to use badsector function

I noted md add a function about badsector.But I did not found how to using.
1:when create a raid5 and superblock is load:

    in function super_1_load:
	 if (sb->bblog_offset == 0)
		rdev->badblocks.shift = -1;

2:when runing raid5,meet badsector. Because shift=-1,not add 3:mdadm can't provide a parameter to set.

Thanks!

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kedacomkernel
2012-02-26